1. Field of the Invention
The present invention relates to agricultural implements, and, more particularly, to agricultural sprayers having at least one onboard tank for holding agricultural chemicals.
2. Description of the Related Art
Agricultural sprayers apply a liquid to a crop or the ground at a specified application rate. The liquid may be in the form of a solution or mixture, with a carrier liquid (such as water) being mixed with one or more active ingredients (such as a herbicide, fertilizer and/or a pesticide). The application rate can vary over different parts of a field through the use of precision farming techniques, such as by using GPS data to activate/deactivate boom sections of the sprayer as the sprayer traverses over the field.
Agricultural sprayers may be pulled as an implement or self-propelled, and typically include a tank, a pump, a boom assembly, and a plurality of nozzles carried by the boom assembly at spaced locations. The boom assembly typically includes a pair of wing booms, with each wing boom extending to either side of the sprayer when in an unfolded state. Each wing boom may include multiple boom sections, each with a number of spray nozzles (also sometimes referred to as spray tips). Of course, a self-propelled sprayer also includes an onboard power plant (e.g., diesel engine) providing motive force and other power such as hydraulic power, electrical power, etc.
Agricultural sprayers may generally be divided into two types or methods of application: a batch application method, and a metered application method. With a batch application method, a tank is filled with the carrier liquid, one or more active ingredients are mixed with the carrier liquid in the tank, and the solution or mixture is applied at a predetermined application rate over the field (defined by vehicle travel speed, nozzle size and fluid operating pressure). A batch application method is effective but is not sensitive to different application needs across the field. Moreover, it is rarely the case where liquid in the tank is not left over at the end of spraying, which then must be discarded. These factors increase the operating costs associated with a batch application method.
With a metered application method, the active ingredient(s) are mixed at a metered rate with the carrier liquid as it is transferred from a carrier tank to the sprayer nozzles. Such metering may be carried out using pumps, venturi nozzles or controllable valves. A metered application method allows the application rate to be more easily changed “on-the-fly” across a field, and avoids the need to dispose of unused spray solution at the end of a spray operation (except what may be left in the lines, pump, etc. between the tank and nozzles).
Conventional sprayers using a metered application method include a carrier tank and one or more active ingredient tanks, all of which are permanently mounted to the sprayer chassis. The carrier liquid is pumped from a nurse tank (e.g., carried on a flat truck or trailer) to the carrier tank on the sprayer using a transfer pump and fill lines. Similarly, the active ingredient(s) are pumped from a nurse tank to a respective active ingredient tank on the sprayer using a transfer pump and fill lines.
What is needed in the art is an agricultural sprayer which can selectively shift the weight distribution and hence the center of gravity of the sprayer.